Nearly 25 percent of America’s electricity now comes from renewables, surpassing coal for the first time. Ten states, and Puerto Rico and Washington DC, have policies in place to run on 100 percent clean power in coming decades. But achieving that goal presents a host of challenges, from updating an aging electricity grid to financing energy innovation to figuring out how to transport and store the renewable power.

America has always prided itself on “thinking big” – from the railroads to the moon landing. Do we have what it takes to pull off the transition from fossil fuels to renewables?